Heat oil and butter together in a heavy skillet or saucepan until butter is melted.
Add the onion and peppers; season with herbes de provence and salt and pepper to taste.
Simmer, stirring frequently, for about 45 minutes, or until vegetables are limp, tender and lightly browned.
Peppers provencal should have a marmaladelike appearance.
Add garlic and basil and cook for another 5 minutes.
Remove from the skillet and let cool to room temperature.
Drain excess oil.
Fill a quiche shell with this mixture, or fill your own little tarts.
We also love it as a vegetable side dish.